Expanding climate policy adoption improves national mitigation efforts

To identify means to improve mitigation efforts, we investigated whether the number of climate policies is associated with emission projections up to 2030 and compared policies’ prevalence across country groups. We find that larger and more comprehensive policy portfolios are conducive to emission reductions, regardless of whether absolute emissions increase or already decline. However, country groups have distinct entry points to expand climate policy. Countries with fast-increasing emissions have significantly fewer policies overall but policies are especially missing in energy-demand sectors, such as buildings and transport. Countries with stalling emissions lack climate strategies and other cross-sectoral policies. This suggests the need for better coordination of mitigation efforts across sectors. In all country groups that fail to reduce emissions, policies to reduce energy and material demand are also substantially fewer. Despite the collective increase of policies in force, countries can still expand climate policy to use the full breadth of mitigation options available.


Supplementary
: Variance inflation factor (VIF) of distinct policy density indicators. The figure indicates that a high number of electricity and heat policies is associated with a high number of policies in other sectors. While a correlation matrix measures one-on-one relationship between policy density indicators, the VIF measure one-to-many relationships and summarises the information in one single value. Here, we use typically-used VIF cut-off values for reference 1 .

Supplementary methods
This section presents a summary of the typology used in the research and example of policies included. This section is adapted from Nascimento et. al 2 .

Policy instrument types
The original typology includes additional instruments since these categories could be further disaggregated. However, further disaggregation resulted in samples too small for statistical analyses.

Policy instrument type Description
Climate strategies Includes, for example, formal and legally binding climate strategies and climate change strategies which are not enshrined in law but are rather adopted through policy documents published by government agencies.

Codes and standards
Codes and standards are a very prominent sub-category of regulatory instruments. They refer to, for example, building codes and standards, industrial air pollution standards, product standards, vehicle fuel-economy and emissions standards

Direct investments
Direct investments differ from fiscal and financial incentives because they refer to direct investments by national governments. For example, they include direct transfer of funds from national to sub-national governments for activities that have a potential to ' GHG Also, infrastructure investments with a mitigation component would also be considered a direct investment.

Fiscal and financial incentives
Fiscal and financial incentives are a specific type of economic instruments that indirectly provide incentives for measures but do not establish a market-based mechanism. Some examples are feed-in tariffs, CO2 and other taxes and subsidies.

Information and education
Refer to policies aimed are informing or educating users. Some examples include consumer-oriented labelling schemes that provide a rating of good or service against a pre-determined scale or that inform that good or products adapts to pre-defined minimum standards related to mitigation outcomes. It also includes schemes aimed at increasing access to information with potential positive mitigation outcomes, such as energy savings approaches or training programs for activities associated directly or indirectly with mitigation outcomes.

Market-based instruments
Includes multiple instruments such as: government-established emissions limits or caps on specific actors which can be traded to incentivize cost-effective emissions reductions; Scheme for the generation of tradable renewable energy certificates, or; schemes for generating tradable energy savings certificates produced by energy efficiency activities measured against a baseline.

Other regulatory approaches
Other regulatory approaches are those which do not fall into the codes and standards category, such as obligation schemes (e.g., mandatory requirement to comply with regular quotas for mitigationrelated outcomes, such as yearly energy efficiency improvements for businesses).

Research and Development
Includes incentive schemes to accelerate the production of near-tomarket technologies, nascent technologies with mitigation potential or the support for the implementation of pre-operational technologies or new uses of existing technologies.

Voluntary approaches
Voluntary approaches include partnerships between public and private actors for the implementation of mitigation-related activities or agreed voluntary commitments. It also includes several schemes to support voluntary activities by private actors, such as providing incentives to overcome split incentives (e.g., between landlord and tenant).

Agriculture
Includes policies to increase sustainable practice in agriculture. Policies associated with sustainability standards for biomass used as a source for biofuels in other sectors are also included in this sector.

Buildings
Includes policies that target energy-use in buildings. These policies address building structure, appliances, cooking and heating/cooling devices. This sector also contains urban planning strategies.

Electricity and heat
Policies related to energy supply and enabling infrastructure, such as transmission and distribution grids, are included in this sector. However, policies related to fossil fuel exploration and production are included in the industry sector.

General
Cross-sectoral policies or policies that apply to any sector and that provide framing for or enable the implementation of other sectoral policies are included in this sector. These include, but are not limited to, national or sectoral climate strategies and Research and Development (R&D) policies.

Industry
Policies covering both energy-generation for own use and process-related emissions. This sector also includes policies related to other non-energy emissions. For example, emissions related to waste or fossil fuel exploration.

Transport
This sector includes policies related to all modes of land transportation and infrastructure programmes that might reduce transport needs (e.g., urban planning).

Mitigation areas Energy service demand reduction and resource efficiency
Includes policies that indirectly reduce demand by supporting activity changes (e.g., reducing material use in manufacturing industries or developing urban planning strategies to minimize transport needs). These policies modify demand for goods and services by targeting choices/adoption of technology, consumption, behaviour, lifestyles, coupled production-consumption infrastructures and systems, service provision and associated socio-technical transitions" 3 .

Energy efficiency
Includes policies to reduce national energy use. Energy efficiency policies include both framing policies with a goal to reduce energy consumption, such as energy efficiency targets, as well as policy options that support energy reductions in specific sectors, such as subsidies for energy efficient appliances or fuel consumption standards.

Renewables
Includes policies to support renewable energy technologies. This support might take a direct form, via subsidies or loans, or indirect, such as by developing grid infrastructure technology, that support the integration of high share of variable electricity generation technologies. This mitigation area includes policies that support the uptake of renewables in energy-use sectors, such as bio-energy mandates in in transport.

Other low-carbon technologies and fuel switch
Includes policies that support non-renewable, low-carbon technologies and options that impose limitations on the use of emissions-intensive technologies. Low-carbon technologies include support for nuclear electricity and fuel switch include for example coal and oil phase out policies. In this mitigation area we also include policies that support carbon dioxide removal technology development.

Non-energy
Includes policies that reduce non-energy related emissions. For example, policies to reduce emissions associated with fossil fuel exploration and production, industrial processes and the ban of fluorinated greenhouse gases.